Do not rely on an <ichc>invisible cast</ichc> to return failure in

Do not rely on an <ichc>invisible cast</ichc> to return failure in
dino_intr_map(); rather than adding the missing cast, make the intent of
the code clearer by explicitenly testing for PCI_INTERRUPT_LINE being ff.

While there, enable the out-of-extent-range checks in dino_memmap() and
dino_memalloc() even if no option DEBUG, but return failure instead of
panicing.

discussed with and ok kettenis@ marco@